Prefabricated multi story stair assembly method

ABSTRACT

A prefabricated multi-story stair assembly in which the supporting members are all confined within the stair unit and which includes means for leveling the stair unit in its preinstalled arrangement and in which the platforms are pivotally mounted on the prefabricated stair unit for rocking movement between an unobstructed raised position to normal horizontal position to form the landing.

Uite States Simmons et a1.

PREFABRICATED MULTI STORY STAIR ASSEMBLY METHOD Inventors: Smith 11. Simmons, Largo; Mitchell R. Caraway, Tampa, both of Fla.

Assignee: The Standard Fabricated Products Co., Clearwater, Fla.

Filed: July 19, 1973 Appl. No.: 380,741

Related US. Application Data Division of Ser. No. 143,115, May 13, 1971, Pat. No. 3,788,018.

US. Cl. 52/741, 182/131 Int. Cl E04f 11/02 Field of Search 52/741, 745, 185, 183;

References Cited UNITED STATES PATENTS 3/1965 Calvert 52/741 X [451 .lan.14,1975

3,228,154 1/1966 Mulitz 52/185 3,393,481 7/1968 Meuret... 52/741 X 3,693,754 3/1972 Butler i 182/115 X 3,707,814 l/l973 Seegers 52/185 3,788,018 l/1974 Simmons et al. 52/185 Primary ExaminerPrice C. Faw, Jr.

[57] ABSTRACT A prefabricated multi-story stair assembly in which the supporting members are all confined within the stair unit and which includes means for leveling the stair unit in its pre'installed arrangement and in which the platforms are pivotally mounted on the prefabricated stair unit for rocking movement between an unobstructed raised position to normal horizontal position to form the landing.

3 Claims, 13 Drawing Figures mgmgu JAN 1 4m;

SHEET 1 OF 6 PATENTEB JAN I 4 I975 SHEEI 2 UF 6 PATENTED JAN 1 M975 SHEET 1 0F 6 PATENTEB JAN I 4 i975 SHEEI' 5 BF 6 FY O Z2 PATENTEB JAN 1 M975 SHEET 8 BF 6 PREFABRICATED MULTI STORY STAIR ASSEMBLY METHOD This application is a division of application Ser. No. 143,115, filed May 13, 1971, now U.S. Pat. No. 3,788,018. This invention relates to prefabricated stairs of multi-story units adapted to be manufactured at a common site for efficiency in mass production and to be transported as a pre-assembled unit to a distant site for installation in the construction of multi-story buildings, such as homes, apartments, motels, office or factory buildings, but it will be understood that the concepts of this invention have application also to preassembled, prefabricated units of from one to a number of stories, compatible with the ability to transport the units from the manufacturing site to the construction site.

It will be apparent from the foregoing that some of the facts controlling commercial success of such prefabricated, pre-assembled multi-story stairway units resides in the ability to effect material savings in the cost of materials and assembly; construction with a minimum of weight to enable economical handling and transportation of the pre-assembled units; assembly into a package which takes up minimum amount of space to enable economical transportation of multiple units on conventional transports from the manufacturing site to the station of use at the building construction site; and to rpovide other advantages from the stand point of stability during installation of the prefabricated unit and its incorporation as an integral part of the building under construction, as well as the ability to stack one unit onto another in building up the stairway as a sequential function in advance of building construction whereby use can be made of the prefabricated, pro-installed stairway as a means for gaining access to upper floor levels in advance of their constructron.

In the latter connection, the prefabricated, multistory stair unit of this invention is pre-installed in position of use in advance of the construction of the corresponding levels of the building whereby the prefabricated, pre-installed stairs becomes available as a means for gaining access to the upper floor levels by members of the building trades thereby to avoid the necessity to construct expensive, time and space consuming scaffolding, temporary ladders, elevators or the like, while providing increased safety by reason of the greater stability and more space available with the prefabricated, pre-installed, multi-sto'ry stair unit of this invention.

As the floors are completed, including the masonry defining the stair well, the structural elements of the prefabricated, pre-installed stair assembly are incorporated by the masonry and other structural elements of the building permanently to incorporate the multistory, pre-installed unit in the stair well of the building to become a permanent part thereof. It will be apparent that as the building construction catches up with the upper levels of the multi-story stair unit, additional units can be stacked one on top of the other to rise above the current level of the building until the stairway rises continuously to the ultimate height of the building.

In present construction of muIti-story stair units, use is made of continuous structural members for support ofthe elements in their prefabricated arrangement with the thought that such continuous stair supports would be concealed within the masonry of the walls to tie the stairs into the building as progress is made in building construction. This imposes a number of limitations with respect to the dimensional characteristics of the prefabricated unit as related to the construction of the stair well, but the need to provide structural supports that fit into the masonry operates undesirably to increase the bulk as well as the amount of material re quired in the prefabricated unit with corresponding increase in weight as well as the dimension and cost of the assembly. Since the support system remains for incorporation into the walls. building costs are increased by reason of the need to construct the perimeters to embed the support members, including the cutting of masonry blocks to embed the support system.

It has been found that often times the foundation or slab on which the prefabricated unit is pre-installed is not perfectly flat or level. As a result, perfect vertical alignment of the stacked stair units is difficult to achieve or to adjust, especially if the stairs have been assembled and stacked but before they are incorporated as a permanent part of the building. This often leads to instability of the stairs and the need to make major reconstructions or repairs.

It is an object of this invention to provide prefabricated stair units which can be pre-installed at the building site; which are capable of economical production on a mass production basis to make available units at less cost at the construction site; which occupy minimum space and make use of a minimum amount of material in the prefabricated unit thereby to enable easier handling of the unit and transportation thereof by conventional transports; which are further characterized by a supporting system which is contained entirely within the stair well and therefore are not required to be embedded in the masonry walls with the resultant minimization of the amount of masonry work and elimination of unnecessary steel support parts; in which certain structural elements such as the landing platform can be folded to provide a prefabricated unit which occupies less space and in which less of the structural elements are exposed to possible damage; in which a minimum amount of bracing is necessary thereby to reduce the cost and weight of the prefabricated unit; which embodies means for self-alignment thereby to permit proper alignment of the installed prefabricated unit substantially independently of the surface or foundation on which the unit is mounted.

These and other objects and advantages of this invention will hereinafter appear and for purposes of illustration, but not of limitation, embodiments of the invention are shown in the accompanying drawings in which FIG. 1 is a side elevational view of a prefabricated, multi-story stair unit embodying the features of this invention with the elements in their arrangement for transport prior to installation;

FIG. 2 is a perspective view in elevation of the prefabricated multi-story stair unit shown in FIG. 1 showing the elements in their pre-installed arrangement;

FIG. 3 is a side elevational view similar to that of FIG. 1 showing the movement of elements from transport position (in broken lines) to installed position (in solid lines);

FIG. 4 is a top plan view of the pivotally mounted platform which defines the landing between stair stringers, when in position of use;

FIG. 5 is a sectional elevational view showing the platform in position of use in solid lines and in partially lowered position in broken lines;

FIG. 6 is a plan view of the lower end portion of the support showing the means for leveling the prefabricated, pre-installed multi-story stair unit;

FIG. 7 is an enlarged sectional view showing the details of the leveling means;

FIG. 8 is an elevational view illustrating the means for connecting additional stacks of stair units one to another in a multi-story assembly;

FIG. 9 is a detailed sectional view showing the interconnection between stacks;

FIG. 10 is a perspective view similar to that of FIG. 2 of a modification in the means for temporary support;

FIG. 11 is a side elevational view similar to that of FIG. 5 but of the platform of the modification shown in FIG. 10;

FIG. 12 is an enlarged sectional view of the platform shown in FIG. 11 in lowered or normal position of use; and

FIG. 13 is an elevational view showing the bracing connections at the stringers.

Referring now to the drawings, description will be made of a prefabricated three-story stair assembly embodying the features of this invention, but it will be understood that the concepts of this invention may equally be employed in one, two, four or other multistory units consistent with the ability to handle the unit and transport the same from the site of manufacture to the building site for installation. Each story section is formed with a platform and 20, adapted to extend horizontally to provide a landing 22 and 22, about midway between the floors 24 and 24 with a lower run of stairs 26 and 26 extending angularly downwardly from about one-half of the inner edge of the platform 20 or 20 to the floor below and an upper run of stairs 28 and 28 extending angularly upwardly from the other half portion of the same inner edge of the platform to the floor above, with the upper run of stairs 28 and 28 offset laterally from the lower run of stairs 26 and 26.

Each stair runner can be of conventional construction. In the illustrated modification, each stair runner is formed of a pair of stringers 30 and 32 in the form of channel irons which are laterally spaced by an amount to correspond to the width of the staircase. The stringers are joined in their laterally spaced apart parallel relation by the risers 34 and the treads 36 which make up the series of ascending steps and which extend crosswise between the inner walls of the stringers 30 and 32. In the preferred practice, the stair risers 34 and treads 36 are each formed of metal plates to anable attachment between the lateral edges of the risers and treads with the inner walls of the stringers, as by welding or other suitable metal attachment means. By way of modification, the risers 34 and treads 36 can be formed of wooden boards, panels, laminates or other structural material adapted to be mounted on metal frame members which can be secured for permanent attachment to the laterally spaced apart parallel stringers.

The prefabricated multi-story stair unit is constructed with a permanent support in the form of a pair of newels 40 and 42, represented in the drawings as a pair of vertically disposed parallel metal members such as steel tubular members, angle iron members or the like which are longitudinally spaced by an amount corresponding to the horizontal distance covered by each run of stairs and dimensioned to have a length corresponding to the total height of the prefabricated, multistory stair unit. One newel 40 extends continuously between the inntermost stringers adjacent the platform end while the other newel 42 extends continuously between the stringers adjacent the floor end, with the newels connected as by welding or other metal fastening means to the adjacent stringers 30 and 32 to provide an assembled relationship therebetween.

At the level where each upper and lower run of stairs meet, a header 50 is secured as by welding to the vertical edges defining the ends of the stringers to extend crosswise thereof. The headers are dimensioned to have a length greater than the combined width of the joined stair sections to provide end portions 52 and 54 which extend laterally beyond the staircase for anchorage into the wall of the stair well, when it is formed, to anchor the prefabricated, pre-installed, multi-story stair assembly in the installed position in the building. The headers 50 are preferably formed of metal structural members in the form of channel irons, with the flat back wall flush with the vertical edges at the ends of the stringers for attachment thereto, as by welding or other fastening means, to join the pair of offset stair sections in their assembled relation and to anchor the sections into the wall.

The longitudinally spaced apart newels 40 and 42 preferably, though not necessarily, can be allowed to remain as a permanent part of the prefabricated multistory stair unit, especially when prefabricated to include railings 60 and 62 which are mounted to run parallel with the run of stairs in vertically spaced apart relation thereto. The railings are secured at their ends to vertically spaced portions of the newels. The railings, which do not form an essential part of the prefabricated assembly, can be installed separate and apart from the prefabricated stair unit, as by attachment to the newels after installation of the stair unit or by mounting the rails on the walls of the stair well after the masonry has been completed.

In the fabricated unit of this invention, it is desirable to provide vertical supports for the outer portions of the stair sections as a supplement to the support provided the inner portions of the stair sections by the newels. Since such other supports become superfluous after the headers 50 have been anchored into the masonry walls, such outer vertical supports can be removed after installation of the stair unit has been completed. By reason of their temporary nature, such additional supports are located within the framework of the stair unit so that the prefabricated multi-story stair assembly can be constructed without external bracing of the type heretofore required, or as a multi-story stair unit in which the supporting system is contained entirely within the framework and therefore free of the walls of the stair well.

Such temporary supports are in the form of angle members 66 or other elongate structural elements which extend vertically between the extremities of the stringers 26 and 26. Support for the bottom run is provided by short angle sections 66 which extend vertically from the upper extremity of stringer 26 and the lower extremity of stringer 28 to a cross brace member 68, in the form of an angle iron, secured to the lower ends of the vertical support sections 66 to rest as a foot on the floor 24. After the described stair assembly has been installed and the headers have been anchored into the adjacent walls, the temporary bracing, as well as the newels other than those on which the railings are mounted, can be removed to provide full access to the stairway.

The basic unit described, with all of the bracing confined to within the frame members, which enables the prefabricated unit to fit entirely within the stair well, represents an important feature of this invention. The platforms 20", etc. can be supplied as separate elements to be mounted crosswise of the inner ends of the upper and lower runs of stairs between the floors. However, another important feature of this invention resides in the construction of the prefabricated multistory stair unit with the platforms 20, 20", etc. mounted as an integral part thereof but in a temporary position, hereinafter referred to as the raised position, whereby the platforms do not materially increase the amount of space occupied by the assembly when packaged for storage or shipment from the site of manufacture to the construction site.

As illustrated in FIGS. 3, 4, 5 and 12, the platform 20 is pivotally mounted at its inner end to portions of the stringers and newel immediately above the header 50 which extends crosswise between the lower and upper runs of stairs between floors, to enable rocking movement of the platform between raised position and lowered position of use. For this purpose, use is made of a continuous, but preferably a plurality of separate laterally spaced apart hinges in the form of butt hinges 70, each of which is formed with a pair of arms 72 and 74, at least one of which is mounted for rotational movement about a horizontal axis or pin 76 parallel with the header. One arm 74 is fixed, as by welding, to the adjacent newel and/or ends of the stringers, while the other arm 72 is fixed, as by welding, to the inner vertical face 78, of a cross-brace member 80, such as an L-shaped angle ironwhich functions as a frame member which extends across the inner end and forms a part of the platform 20. In the preferred practice, the pivot 76 is located above the upper horizontally disposed flange 82 of the header 50 by an amount corresponding to the distance between the pivot and the lower horizontally disposed flange 84 of the platform frame member 80 so that the latter will come to rest on the horizontal surface of the header flange 82 when the platform is rocked to its lowered position. In its packaged position for storage or shipment, the platforms are adapted to be retained in their raised position, as illustrated in FIG. 1, by temporary tie means such as wires, chains, rope and the like. Means can be included for lowering the platform from its raised to its lowered position of use to form the landing. Such means may include a chain, as illustrated in FIGS. 5 and 11, anchored at one end to the far end of the platform while the other end can be manipulated from the stairs. The same chain can be used as the tie means for latching the platform temporarily in its raised position.

The platform 20 itself is of conventional construction including a corrugated steel deck 86 fastened onto the upper surface of spaced apart beams 88 secured at their inner ends to the upper surface of the flanged portion 80 of the frame plate and at their outer ends to the upper surface of a platform support header 90, in the form of a steel channel member which extends continuously crosswise beneath the outer end of the deck and beyond the platform to provide anchoring sections 92 which are adapted to become embedded in the masonry walls for support of the platform in the installed position of use. The metal deck portion is conventionally covered with cement or paneling to provide the cross-over landing between the opposite runs of stairs between the floors.

Means are provided temporarily to support the platforms when rocked to their lowered positions. In the modification shown in FIGS. 2, 3 and 4, the temporary supports are in the form of elongate rods 94 dimensioned to extend angularly between the outer end portion of the lowered platform 20 and the lower portion of temporary support 66. The upper end of each of the supporting rods 94 is provided with a means for anchorage with the platform for stabilized support thereof. In the modification illustrated in FIGS. 3 and 5, the anchorage means comprises a pin 96 which extends angularly from the rod in the vertical direction for insertion into a socket opening 98 in the far end of the angle supports or beams for the platform to enable the pin to be received in the socket opening as the platform comes to rest on the end of the rod for support.

The support for the lowermost platform 20 comprises a pair of laterally spaced apart tubular members 100 fixed at their lower ends to a foot 102 in the form of a crosswise extending angle iron which rests on the floor while the platform rests on the upper ends of the vertical rods 100 when lowered to position of use.

In practice, after the prefabricated multi-story stair unit has been installed in its proper upright position, the tie for the pivotally mounted platform is released and the chain 104 is paid out to enable the platform to rock gravitationally about its pivot 76 to the lowered position. The angular supporting rods 94 are braced at their lower ends against the vertical brace 66 while the pin 96 at the upper end is held in position to enter the socket 98 as the platform is let down to lowered position until the platform comes to rest on the end of the tubular support member which thereafter is effective to retain the platform in the desired horizontal position until the ends of the platform headler become anchored in the masonry of the adjacent walls. Thereafter, the tubular supports can be removed and the stairway finished by covering the platforms landing material.

In the modification illustrated in FIGS. 10, 11 and 12, the temporary supports for each of the platforms 20 comprise a pair of laterally spaced apart tubular members dimensioned to have a length corresponding to the space between the ground and the first platform 20 and other tubular members 112 dimensioned to have a length corresponding to the distance between platforms, when in their horizontally disposed position. The lower ends of the lower pair of tubular support members 100 are fixed to a horizontally disposed crosswise extending angle iron 114 which is adapted to rest on the floor as a foot. The upper ends of the tubular members 110 and 112 are provided with pins 116 of lesser cross-section than the internal bore of the tubular members with the pin being welded to the ends of the tubular members to extend a short distance beyond the ends thereof. The brace elements 88 adjacent the lateral edges of the platforms 20 are provided with passages 98 dimensioned to have a cross-section greater than the cross-section of the pin 116 but less than the cross-section of the tubular support 110 or 112 to enable the pin 116 to extend therethrough.

In assembly, the lowermost pair of tubular support members 110 are held in position to enable the pins 116 to penetrate through the socket openings 98 as the platform comes to rest on the tubular support when rocked to its lower position of adjustment. Before the platform at the next level is lowered to position of use, a pair of elongate support rods 112 are positioned in vertical alignment with the rod 110 with the lower ends of the tubular members 112 telescoping over the pins of the preceding rods which project into the socket openings of the platform. Thus the tubular members 112 are vertically aligned in position to enable their pins 116 to penetrate through the socket openings as the above platform is lowered onto the rods in position of use. This procedure is repeated as the upper platforms are progressively lowered to landing position. After the laterally projecting end portions of the platform channel headers 90 are anchored into the walls of the stair well for permanent support of the platform, the tubular members 110 and 112, which function as temporary supports, are removed as by bending, cutting or otherwise disengaging the tubular members from their telescoped relation. Unless the newels have the inner railing mounted thereon, they too can be removed. This leaves the stairway installed, with or without the newels 40 and 42 as internal supports, and the embedded headers as external supports for the stairway in its installed relation.

As previously pointed out, the prefabricated, multistory, stair units can be stacked one on the other to enable utilization of such prefabricated units throughout the height of a multi-story building. Means are provided for securing the stacked units one to another in their stacked relationship.

For this purpose, as illustrated in FIGS. 8 and 9, the upper end 115 of the lower stack 117 and the lower end 118 of the upper stack 120 are provided with lengthwise extending, laterally spaced apart, horizontally disposed angles 122 and 124 having aligned openings 126 in their horizontally disposed meeting flanges 128 to enable one angle member to be bolted down to the other, as by means of the nut 130 and bolt 132 fasteners illustrated in FIG. 9.

It has been found that often times the floor or slab on which the prefabricated unit is installed may be uneven or sometimes the unit or building settles after installation of the prefabricated stair assembly but before it is incorporated into the building, with the result that the installed unit is not'in proper vertical alignment for permanent attachment to the building. Various means which have heretofore been employed to effect alignment, such as shims, have been difficult to install and angular adjustment thereby has been difficult to control.

Thus, it is a further important concept of this invention to provide a simple and efficient means by which the prefabricated multi-story stair unit of this invention can be adjusted after installation for effecting proper vertical alignment, even though the foundation is uneven or deviates from the horizontal. For this purpose, the angle irons 68 and 138 between the lower ends of the vertical supports 66 and the newels 40 and 42 are provided with spaced openings 140 through the horizontally disposed flange portions 142. The openings themselves can be threaded but it is preferred to make use of a threaded nut member 144 secured to the flanged portion in registry with each opening. Threadably engaged in each of said threaded nut members or openings is an elongate bolt 146 having a tool-engaging head portion 146 uppermost. The prefabricated unit is installed with a portion 150 of the bolt extending downwardly beyond the opening so that the assembly will rest for support on the through-extending portion of the bolts. When the prefabricated unit has been installed, but before the headers are incorporated permanently into the masonry walls, angular adjustment of the unit is effected by turning one or more of the individual bolts 146 in one direction or the other depending upon whether or not it is desired to raise or lower the particular section of the assembly to compensate for differences in level or angle. The through-extending end portions of the leveling bolts are preferably provided with shoes 152 to distribute the load.

In practice, the elements making up the assembly are preferably formed of metal members assembled together as by welding, with all but the temporary tubular supports for the platform included as a part of the prefabricated assembly. The platforms are tied in their raised position to provide a package that occupies minimum space for transportation to the building construction site.

At the site, the prefabricated stair unit is stood upright on a pad or foundation, as by means of a suitable gantry or crane, to position the prefabricated unit upright for installation. When properly positioned, the tradesmen can release the first platform which is then lowered by the chain onto the lower tubular supports until the pins enter the sockets and the platform comes to rest on the support. The platform at the next level is released and is lowered by the chain onto the next pair of tubular support members until the pins enter the sockets as the platform comes to rest on the tubular support and this is continued until all of the platforms have been lowered to horizontal position to define the landings.

Thereafter, the assembly is leveled by proper adjustment of the leveling bolts 146 and the pre-assembled, prefabricated multi-story stair unit is ready for permanent installation in the building by anchoring the lateral portions of the headers 50 in the masonry or walls which define the stair well. After installation and anchorage of the headers, the temporary tubular supports are removed to leave the installed stairway free of exposed bracing. The treads, risers and platforms can be covered in the usual manner with boards, cement and the like to provide the permanent installation.

In the meantime, the prefabricated, pre-assembled and pre-installed multi-story stair unit which extends vertically upwardly beyond the floor level is available for use by the tradesmen for access to construct the upper level of the building whereby the multi-story stair unit enjoys considerable utility of great value even before the walls of the stair well are built for permanent installation of the stairway into the building.

As previously described, one unit can be stacked on another as the building progresses whereby a continuous stairway is provided which projects upwardly beyond the current level of the building for use in construction of such upper levels or to gain access to such upper levels as they are being built.

Thus, the stairs are set in position prior to the construction of the masonry walls thereby affording the various construction trades immediate access to all floor levels as the construction progresses.

It will be apparent from the foregoing that the stairway assembly embodying the features of this invention represents a unit formed of a supporting system which is confined entirely within the stair well walls thereby to reduce the amount of masonry work required for installation and minimize the amounts of steel structural supports required for the assembly. The temporary tubular bracing members for the stair sections are all confined within the stair well to provide unblocked accessibility for mounting the stair case. It will be understood that changes may be made in the details of construction, arrangement and operation without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. The method for installation of the multi-story prefabricated stair unit comprising opposite runs of at least one pair of laterally spaced apart flights of stairs with the upper end of one flight and the lower end of the other flight alongside one another at about midway be tween the height spanned by the flight, headers formed at the ends of each flight of stairs and dimensioned to have a length greater than the width of the laterally offset pairs of stair flights to provide a portion extending laterally beyond the stairs for anchorage into walls, newels extending vertically between the laterally offset flights of stairs and joined thereto to provide a central internal support for the assembled flights of stairs, means for mounting a platform to extend horizontally outwardly from the upper end of the one flight and the lower end of the other flight at a level with said ends midway between the height spanned by the flights in which the platform is pivotally mounted with respect to the meeting ends of the lower and upper flights of each pair for rocking movement between raised and normal horizontal position and which includes a cross brace member secured to the underside of the platform to extend crosswise thereof beyond the pivot and having portions projecting laterally beyond the platform for anchorage into adjacent walls of the building, and temporary supports engaging the portions of the platform beyond the pivot when in horizontal position for temporary support of the platform in its pre-installed relation, the method comprising positioning the prefabricated multi-story stair unit to extend vertically from a supporting base, lowering the platform to horizontal position, engaging the platform when lowered to horizontal position with the temporary supports for support of the platform in horizontal position, anchoring the laterally extending portions of the support members in the adjacent walls of the stair well as they are formed and then removing the temporary supports for permanent installation of a multi-story stair unit in the buildmg.

2. The method as claimed in claim 1 in which the temporary supports for the platform comprise laterally spaced socket openings in the underside of the platfomr in the outer portions thereof away from the pivot, elongate rods extending angularly inwardly from the socket openings to adjacent the underlying vertically disposed support members and a pin at the end of each of the elongate rods adapted to be received in one of said openings when the platform is in normal horizontal position, comprising positioning the elongate rods with the lower ends in abutting relationship with a horizonta] portion of the support members: or adjacent portions of the stairway while maintaining the rods to position the pins at the opposite end for entry into the platform openings when the latter is lowered to horizontal position and lowering the platform until the pins enter the openings.

3. The method as claimed in claim 1 in which the temporary support for the platform comprises laterally spaced apart openings in the platform in the portions beyond the pivot, elongate tubular members dimen sioned to span the space between adjacent horizontally disposed platforms and having a cross section greater than the cross section of the platform opening, and a pin in the upper end of each tubular member dimensioned to have a cross section less than the cross section of the platform openings to enable projection therein and less than the passage in the tubular member for enabling telescoping therein whereby the platform rests on the end of the tubular members adjacent the underside thereof with the pin extending through the opening while the tubular members are vertically aligned one with another with the lower end of each tubular member above the lowermost being telescoped onto the pin for alignment and support with the tubular member beneath, positioning the tubular support members for the lower platform in vertical alignment with the openings of the platform when in horizontal position, lowering the lowermost platform to horizontal po sition with the pins on the ends of the tubular support members extending through the openings, positioning the superposed support members for the next platform onto the tubular members beneath with the pins telescoped into the lower ends of the tubular members, and then lowering the corresponding platform to horizontal position with the pins on the upper ends of the tubular members extending through the platform openings for support. 

1. The method for installation of the multi-story prefabricated stair unit comprising opposite runs of at least one pair of laterally spaced apart flights of stairs with the upper end of one flight and the lower end of the other flight alongside one another at about midway between the height spanned by the flight, headers formed at the ends of each flight of stairs and dimensioned to have a length greater than the width of the laterally offset pairs of stair flights to provide a portion extending laterally beyond the stairs for anchorage into walls, newels extending vertically between the laterally offset flights of stairs and joined thereto to provide a central internal support for the assembled flights of stairs, means for mounting a platform to extend horizontally outwardly from the upper end of the one flight and the lower end of the other flight at a level with said ends midway between the height spanned by the flights in which the platform is pivotally mounted with respect to the meeting ends of the lower and upper flights of each pair for rocking movement between raised and normal horizontal position and which includes a cross brace member secured to the underside of the platform to extend crosswise thereof beyond the pivot and having portions projecting laterally beyond the platform for anchorage into adjacent walls of the building, and temporary supports engaging the portions of the platform beyond the pivot when in horizontal position for temporary support of the platform in its pre-installed relation, the method comprising positioning the prefabricated multi-story stair unit to extend vertically from a supporting base, lowering the platform to horizontal position, engaging the platform when lowered to horizontal position with the temporary supports for support of the platform in horizontal position, anchoring the laterally extending portions of the support members in the adjacent walls of the stair well as they are formed and then removing the temporary supports for permanent installation of a multi-story stair unit in the building.
 2. The method as claimed in claim 1 in which the temporary supports for the platform comprise laterally spaced socket openings in the underside of the platfomr in the outer portions thereof away from the pivot, elongate rods extending angularly inwardly from the socket openings to adjacent the underlying vertically disposed support members and a pin at the end of each of the elongate rods adapted to be received in one of said openings when the platform is in normal horizontal position, comprising positioning the elongate rods with the lower ends in abutting relationship with a horizontal portion of the support members or adjacent portions of the stairway while maintaining the rods to position the pins at the opposite end for entry into the platform openings when the latter is lowered to horizontal position and lowering the platform until the pins enter the openings.
 3. The method as claimed in claim 1 in which the temporary support for the platform comprises laterally spaced apart openings in the platform in the portions beyond the pivot, elongate tubular members dimensioned to span the space between adjacent horizontally disposed platforms and having a cross section greater than the cross section of the platform opening, and a pin in the upper end of each tubular member dimensioned to have a cross section less than the cross section of the platform openings to enable projection therein and less than the passage in the tubular member for enabling telescoping therein whereby the platform rests on the end of the tubular members adjacent the underside thereof with the pin extending through the opening while the tubular members are vertically aligned one with another with the lower end of each tubular member above the lowermost being telescoped onto the pin for alignment and support with the tubular member beneath, positioning the tubular support members for the lower platform in vertical alignment with the openings of the platform when in horizontal position, lowering the lowermost platform to horizontal position with the pins on the ends of the tubular support members extending through the openings, positioning the superposed support members for the next platform onto the tubular members beneath with the pins telescoped into the lower ends of the tubular members, and then lowering the corresponding platform to horizontal position with the pins on the upper ends of the tubular members extending through the platform openings for support. 